Frequency of treatments question...

How do we know if we are given 30 treatments of radiation and really we only needed half that amount and now we have damage to other vital organs. We have to just trust the doctor right? But radiation is his business it's his way of making a living. So how do we know if the treatment is really necessary to be that long or that extreme? I would hate to know that I only needed a dozen treatments and end up with a huge number only because the new cancer center was recently built and needed business. I don't mean to sound like a pessimist but honestly it's all about money. Cancer is big business. Many of us do not have insurance so we have to pay out of pocket.

How do we tell the doctor no I think 30 visits or whatever he gives you is too many. But he's the doctor. How do we get what is really right for US the patient?